Method for detoxifying castor bean proteins



Apr-nl E0, H951 H. F. sAuNDERs METHOD FOR DETOXIFYING CASTOR BEAN PROTEINS Filed Sept. l1, 1947 Zwm KORWTU ATTORNEYS Patented Apr. 10, 1951 UNITED STATES PATENT oFFicE Harold Fn Saunders, Shaker Heights, Ohio, asl,

signor to The Sherwin-Williams Co., Cleveland, f

Ohio, a corporation of Ohio" Application September 11, 1947, Serial No. 773,482

14 Claims. (Cl. 260-123.5)

This invention relates to processes for preparing substantially non-toxic, proteinaceous materials from castor beans and to the products of such processes. More particularly it relates to processes for preparing such products which are readily and easily dispersible in aqueous liquids.

The meal or residue remaining after the extraction of oil from the castor bean normally Y contains substances toxic to bothhumans and animals. One of these substances is an albumin type of protein called ricin. In addition the bean contains small quantities of ricinine, a toxic alkaloid of the pyridine series; and also some allergens. l

-After the oil has vbeen extracted `from the castor bean, a cake or pomaceremains which contains large quantities of proteinaceous ma terials, cellular material, cortex, unless removedV initially, carbohydrates, the above mentioned toxic substances and small amounts of other compounds. If a solvent extraction process were used for recovering the oil, a portion of the solvent will also be present in the pomace or residue.

In order to prepare suitable proteinaceous products from this residue, it is imperative to eliminate the toxic substances, either by removing them as such or by'converting them by decomposition to non-toxic and harmless substances.

. Several methods for detoxifying `the castorV bean residue has been used in the past but all of these methods entail various disadvantages. For example, when attempting to remove ricin from the residue by leaching with boiling Water, a large proportion of the desirable proteins and proteoses are also removed and the removal of the ricin is incomplete. the ricin is carried out at high temperatures, the dispersibility and solubility of theV protein products is largely destroyed, thus rendering the product useless for many purposes. Furthermore, the proteinaceous materials are degraded to Such an extent that they are unfit for use as emulsion stabilizers and the like.

According to the present invention, these disc 2 capable of being removed by merely Washing the residue with hot water, this method is unsatisfactory since the ricin, as with other types of proteins, clings to or is enmeshed or occluded with other proteins so that it cannot be removed solely by Washing. It has been found, however, that the ricin can be dispersed to a high degree and thusV become vulnerable to treatment under mild conditions, when a large proportion of the alkali-soluble proteins in the residue are in a' dispersed phase. Under these conditions the ricin maybe convertedto harmless substances,v by merely heating the dispersion to a relatively.v low temperature which will notseriously aiect the -properties of the proteins.

The first stage of the present process is, there- 80 C. to about 95 C. to effect the detoxication; A,

These temperatures will have little or no degrading effect on the proteins. Y After the detoxification by heating, the dispersion can be treated with an acid, or an acid reacting compound to neutralize or acidfy the dispersion so that a maximum quantity of the solubilized proteinaceous material will be precipitated. If desired, the detoxied dispersion' `Y may be filtered or centrifuged to separate miscellaneous solid materials prior to the treatment When destruction of advantages are overcome and a substantially detoxifying the castor bean residue by heating the same at atmospheric highly dispersed state.

i Although ricin iswatersoluble and lshould be d pressure while in a with acid to precipitate the solubilized proteins; Also, if desired, these miscellaneoussolids'can be separated from the dispersion prior to the detoxication step.

"After detoxification, precipitation (with orV without prior removalof miscellaneous solids) and removal of all or aV large proportion of the remaining water or aqueous liquid by settling, filtering or centrifuging, a detoxied product 'is' 'obtained in which the proteinaceous materials aresubstantially undegraded and have the desired properties and characteristics.

The invention which is illustrated in the accompanying ow sheet will now be described in greater detail.- y v It is preferred tostart with pomaces or residues from oil extraction processes in which the lcastor bean has been decorticated prior to oil 1 extraction. It is to be understood, however, that the employment of pomaces from undecorticated castor beans is within the scope of the present invention since the presence of cortex does not im-f l liquid. solvent-wetted castor pomaces can be employed pair'the usefulness of the nal composition for certain purposes, such as fertilizers or binders for plastics, Where color and insoluble particles are not a consideration. When dispersions are made up from pomaces containing cortex, a dark brown coloration is present and, although the cortex is insoluble, the product may be used in certain applications.

The pomace remaining after extraction of the oil from castor beans is treated with Water and alkali. The quantity of waterzfused is vpreferably suicient to produce about a 1% to about a 3% protein solution, calculating the Aprotein content as 6.25 times the nitrogen content. (The Official and Tentative Methods of -the Association of f Official Agriculture Chemists, fourth edition, 1935, page 355). At about 5%:protein concentration the proteins do not appear to b e ina sumciently dispersed state to detoxify easily, probably being to a considerable extent entangled in the cellular components. BeloW '1% the quantity of Water is too great for economical process- The alkali 'has a number rof functions. -lits presen-ce retards or prevents the 'tendency of vthe pomace to agglomerate 'into lumps when mixed with 'the Water. It aids "In opening up the cellular structure and 'freeing the proteins. It solubilizes and disperses the alkali-soluble proteins. It controls and retards the coagulation of vpro,- teins under the temperatures involved. Dispersions .ofproteins in Water tend to .coagulate when heated to temperatures above about 55 C., and these coagulates are not easily redispersed in alkaline solutions. The coagulation, however, is inhibited by the alkali. ,As 'the pH value of the aqueous dispersion of castor .protein increases above 7.0 pH the vtemperature .at which the ,Coagulation takes lplace rises, so that with a pH value of from about 9 to 11 the solution will Withstand a temperature lof .90 C.. or even higher without visible coagulation. It is, therefore,

" preferable to add .sufficient alkali .togive the mix.-

ture a pH value of from Aat least .9 Iand preferably about 11. .pH values above 11 maybe ,used to secure .a higher .degree of Aprotein ,solubilization but such pH values .have adverse .effects on `the proteins. It .is generally sufficient .to .stir .the mixture for ,about `minutes .in order to -obtain an adequate 4dispersion of the proteins. .Sodium hydroxide is the preferred dispersing alkali .but any soluble alkali -or :alkaline 'salt or .combination thereof may be used satisfactorily, i. e. 1pc tassium hydroxide., ammonia, sodium, or potassitum 'carbonated alkaline :sulphites or .sulphates e c.

The vpomace resulting from solvent extraction processes 'forrecovering the oilisvvetted with the solvent employed. inany co-pending patent application, Serial No. '773,481, now YPatent No.

2,502,484, a method has beendescribedzfor recovering solvent Afrom :such solvent-wetted pomaces Without passing through a dry state .by the use of temperatures 'of faroundf35 C. to '40 fC. 'under partial vacuum while mixed with an :aqueous This method Y'for Ydesolventizing the with the aqueous alkaline dispersion of the pomace inthe present process.

It is not essential when carrying outthe present process to completely remove all of the solvent before proceeding with the detoxification of the castor bean Apomace, since the temperatures 'of the subsequent steps-'of this process willA A. assist in driving off any solvent which might still be present.

The suspension or slurry is now composed of insoluble cellular components of the castor.bean, alkali-insoluble proteins and cortex (if undecorticated beans Were employed) in a dispersion of water-soluble and alkali-soluble protein and other Water-soluble compounds. This suspension is then heated preferably to 90 C. and held at 'that temperature With agitation for a short period ,-suchas `,5 .to about 25 minutes. Usually about 15 minutes is sufficient to effect complete detoxification.

After heating Athe dispersion, the toxicity of 'the ricin and alsothe ricinine is destroyed, thus rendering the mixture non-toxic and safe to use for .a multitude .of purposes, previously excluded.

The dispersion or slurry is then cooled to beloW about C. and acidified with dilute acid to a pH value of from about 3.8 to about 4.0 which causes maximum precipitation of .castor proteins. If acidification is carried out above about 60 C., the proteins tend to coagulate and are not easily redispersed in alkaline solution;

' The solids in the suspension now consist principally of Ithe cellular components of the castor bean, the alkali-insoluble proteins, and the acidprecipitable proteins. The non acid-precipitable proteins, proteoses and the like remain in solution, together with other water-soluble compounds. The solids are then separated from the liquids by filtration or centrifuging, Washed vwith water acidied to about '3.8 to 4.0 pH, dried and, if desired, pulverized, or preferably, left as a water-wetted composition Which may be protected against putrefaction by the addition of a protein preservative such as the sodium salt of chlorinated phenol.

As an alternative procedure, the suspension or slurry, after being heated to about C., may be directly claried, as by filtration or centrifuging. The solids in this case consist principally of the cellular components of the castor bean and the non-alkali soluble proteins. These solids may be dried and are useful as a fertilizer material. The liquids may then be cooled below about 60 C. and acidied with dilute acid to precipitate proteins. This protein precipitate is separated from the liquid in which the non acidprecipitable proteins and other Watersoluble compounds are dissolved. The protein material is then Washed with Water, dried and pulverzed. or it may be left in the water-Weit@ state. ,In vanother alternative procedure, the suspension or slurry may be clarified before the step of detoxifying by heating to about 90 C. The clarification of the slurry may be effected by iiitering or centrifuging and the like.

.For acidifying the liquids. dilute Sulphuric acid may .be used but any other inorganic or Qrgani.

acid which will ,precipitate the .protein ,may be used, such as hydrochloric, sulphurous or acetic acid. Acidic salts, SO2 gas, etc. may also be used.

To more clearly describe the present invention, reference will novvl be made to the following il- 1 lustrative examples:

Example 4I vmixture became fluid. Additional pension was then-further heated to 906 C. at

atmospheric pressure and held at 90 C. for 1 5 minutes, after which it was cooled to 50 C'. and acidiiied to 3.9 pH by the addition of a sulphuric acid solution. The solids were separated from the liquid in a solid bowl centrifuge, washed with water acidii'led to 3.9 verized.

The dried solids analyzed 14.1% nitrogen (88% protein) and contained the ne structured cellular component of the castor bean kernel. This proteinaceouscomposition was of excellent light color, easily dispersible in alkali at 9 pH and substantially non-toxic. The cellular component 10H, dried and puldid not solubilize in the alkaline solution but was in such an exceedingly rlne state of division that it was uniformly dispersed and gave no lappearance of specks when spread as a lm on glass.

The toxicity was determined by feeding to rats When rats were fed a ration composition 'cone' sisting of 5% of the original castor pomacefand 95% of an accepted commercial animal Vfeed containing dried meat, dried sh, bone .meal and or cereals, they showed external symptoms of poisoning within a few hours, i. e. hunched posture, matted fur, nasal discharge, diarrheaand die Vwithin 12 to 24 hours.

With a similarly prepared ration in which the original castor pomace was replaced by the solid composition, prepared as described in this example, the animals did not show lthese symp' toms and continued to live and grow at normal Vrate with normal food consumption. The per-- centage of the castor composition may be increased from 5% to 10% with similar eiect although above 10% the ration appears to be unpalatable.

Emample II A heptane-wetted pomace resulting fromthe `extraction of oil from decorticated castor beans withheptane was desolventized by drying in thin layers at about 70 C. Tothe dry pomace .was added a small amount of aqueous solution of sodiumhydroxide of 11.0 pH value, further-slow addition of the solution was made uritilfthe solution was then `added until the total quantity of solution reached an amount equivalent to fifty times the weight of proteins in the pomace, calculating the protein content as 6.25 times the nitrogen content. The ymixture was then thoroughly-homogenized by circulation through a rotary pump and the pH value was corrected to 115,0- as in Example I. The mixture was then heated lby direct steam to 90 C. while'agitating and this temperature was maintained for 15 minutes. The insoluble residue was removed from the liquid and dried. The solids contained 3.4% `protein, the balance being principally cellular material and is useful asa fertilizer or a binding material.

The clarined nquid was' vcooledfweo" c. and

a 5% solution of sulphuric acid added slowlyv with agitation until a pH of 3.9 was obtained. The precipitate was separated from the liquid, washed with water acidifed to 3.9 pH, dried and 'pulverized The remaining liquids contain the treated, effectiveness of the dispersing step, de- "gree of alkalinity maintained and other factors. .Generally castor compositions preparedas descrbed will contain between 75% and 90% of Y proteins -calculated as nitrogenv times 6.25, the balance being principally cellular matter in exceedingly fine state of division (and -cortex if unf decorticated beans `were taken). The allergens of castor beans appear to be soluble in water and are removed with the liquids and wash waters under the conditions described, so that the products exhibit substantially no allergenic properties.

It is -known that ricinine is decomposed by sulfuric acid, so that whatever portion of this alkaloid is not destroyed by the heating step will be decomposed by the later acid precipitation of proteins. f

Although the present invention has been described with specic reference to particular examples, it will be understood that various modiflcations and variations in the process which would be apparent to one skilled in the art are not excluded and that the scope of the present invention is defined by the appended claims.

What is claimed is: l. A process for treating castor bean pomace to eliminate toxins comprising mixing the pomacewith an aqueous alkaline solution to solubilize at least a portion of said pomace and heating the solution containing the solubilized portion to a temperature Within the range of from about 80 C. to about 95 C. to destroy said toxins.

2. A process as claimed in claim 1 wherein undissolved matter in the mixture of pomace and aqueous alkaline solution is separated from the solution prior to heating to destroy the toxins.

3. A process as claimed in claim 1 further comprising separating undissolved matter from the solution after heating to destroy the toxins.

4. A process as claimed in claim l wherein the mixture of pomace and aqueous alkaline solution has a pl-Irvalue of from about 7.0 to about 11.0.

5. A process as claimed in claim 4 wherein the pH value is from about 9.0 to about 11.

6. `A'process as claimed in claim 5 wherein the pH value of the mixture is 11.

7. A process as claimed in claim 1 wherein thev aqueous alkaline solution comprises an aqueous solution of sodium hydroxide.

8. .A process as claimed in claim 1 further comprising acidifying the solution following the heating step to precipitate solubilized material in said solution.

9. A process as claimed in claim 8 wherein the solution is acidied to a pH of from about 3.8 to about 4.0.

10. A process as claimed in claim 8 wherein the solution is cooled to a temperature below about 60 C. prior toacidication.

.fromabout 1% to ,about 3%, vheatingsaid mixture 4tororrl :about- SONG to about-95 .C. for Va.

periodicifromaboutmnutes toabout 25 minutes to destroy said toxins, cooling said detoxivfled dispersion :to .a temperature nothigher than .6,0" 'C.,;ad,ding fsuicient acidic;l substance to lower 4the pHvalue :to irom about `vrif-3 t0 about .4 to .precipitate ra large :proportion of Ythe solubilized .proteinaceous fmaterial, andseparating atleast .a portion of theliquids fromthes'olids:including the precipitatedg-materia1- y y 1.3. .A process as claimed in .claim 112 wherein those :solids present are vremoved from .the

persion after ithe detoxification step and-privi to the acidicationstep.

14. A process as claimed in claim 12 wherein those solids present are lremoved from thevdis. Apersion prior-to the ldetoxification step. Y HAROLD F. SAUNDERS.

,REFERENCES CITED The ffollowing yreferences are of vrecord i'the le of lthis patent:

UNITED STATES PATENTS Number .Name Date .1,866,698 ,Bronsztajn July v12, 1932 2,233,213 -Knseley etal. .Feb..25, 19.41 2,238,329.. .Julian 617x211.. Apr. .15 .19,41 2,331,619 Morse v Oct. l12, .1943 2,467,402

Pascal Apr. 19, .19.49 

12. A PROCESS FOR TREATING CASTOR BEAN POMACE TO ELIMINATE TOXINS COMPRISING MIXING THE POMACE WITH THE AQUEOUS ALKALINE SOLUTION TO FORM A DISPERSION HAVING A PH VALUE OF FROM ABOUT 9 TO ABOUT 11, THE AMOUNT OF SOLUTION ADDED BEING SUFFICIENT TO PRODUCE A PROTEIN CONCENTRATION OF FROM ABOUT 1% TO ABOUT 3%, HEATING SAID MIXTURE TO FROM ABOUT 80* C. TO ABOUT 95* C. FOR A PERIOD OF FROM ABOUT 5 MINUTES TO ABOUT 25 MINUTES TO DESTROY SAID TOXINS, COOLING SAID DETOXIFIED DISPERSION TO A TEMPERTURE NOT HIGHER THAN 60* C., ADDING SUFFICIENT ACIDIC SUBSTANCE TO LOWER THE PH OF VALUE TO FROM ABOUT 3.8 TO ABOUT 4 TO 